Activation of the macrophage A2b adenosine receptor regulates tumor necrosis factor-alpha levels following vascular injury.

The control of expression of tumor necrosis factor-alpha (TNF-alpha) impacts a variety of processes during a stress response. Macrophages are a major source of TNF-alpha, the level of which is known to be regulated by adenosine. Previous studies highlighted the role of the A2a adenosine receptor in this process, while the role of the A2b adenosine receptor (A2bAR) has not been clearly identified. Here, we examined the contribution of the A2bAR to TNF-alpha regulation by macrophages at baseline and under vascular stress. We employed a newer A2bAR-selective ligand, BAY 60-6583 in vitro and in vivo, and an A2bAR antagonist CVT-6883, as well as examined macrophages derived from control or A2bAR knockout mice. We found that the expression of the A2bAR is upregulated in macrophages derived from wild-type mice subjected to arterial injury, and this receptor activity controls the level of TNF-alpha released from macrophages. We identified a significant role for the A2bAR in the regulation of TNF-alpha, which would contribute to the anti-inflammatory actions of adenosine under vascular stress. This conclusion could focus attention on this receptor as a therapeutic target.